Current controlling device



Dec. 29, 194 J. M. HEDDAEUS CURRENT CONTROLLING DEVICE Filed Feb. 20, 1959 1N VEN TOR Pa tented Dec. 29, 1942 amaze coaamvr comoumc mzvrcn John M. Heddaeus, Detroit, Mich, assignor, by

mesne assignments, to Edward 8. Evans,

troit, Mich.

Application February 20, 1939, Serial No. 257,487

13 Claims.

The present invention relates to means for rapidly and recurrently increasing and decreasing the flow of electrical current in a circuit, and, in the herein disclosed embodiments, is particularly directed to improvements upon the structures disclosed in Schimkus application Serial No. 179,893, filed December 15, 1937, now Patent No. 2,163,709, granted June 27, 1939, and in its parent Schimkus and Dumke application, Serial No. 4,056, filed January 30, 1935, now Patent No. 2,163,708, granted June 27, 1939.

Generally speaking, the above identified applications disclose a device wherein a column of mercury of substantially greater length than width is subjected to the flow of an electrical current, the cross-sectional area of the column being so proportioned relative to the amount of electrical energy which is transmitted through the device, that the current causes a part of the mercury in the column to be converted from the liquid phase, in which it is a relatively good conductor, to a vapor phase, in which it is a relatively poor conductor. The conversion, by increasing the resistance current flow through the device either interrupts or so far reduces the flow of current, and consequently the heating action, that all or part of the vaporized mercury recondenses into the liquid phase, thereby either partially or entirely restoring the original conductivity of the column. The partial or entire recondensation of mercury causes an increase in or resumption of the current flow, thus again causing the above mentioned conversion to the vapor phase. The device is thus effective to translate the output of a direct current source, such as a b ttery, into a pulsating current, h'aving current variations of substantially uniform magnitude and frequency.

The present invention is directed to improvements upon the above structures, whereby the magnitude as well as the frequency of the pulsations may be made more uniform; whereby the may be manufactured and assembled extremely economically,- and which is reliable and eflicient in operation; to provide such a device characterized as embodying a column of material having the property of changing, in response to increases and decreases in applied heat, between conditions in which it is a relatively good and a relatively poor conductor, characterized in that the point in the material at which the transition occurs, is

' confined and controlled; to provide such a device in which transition involves changing between liquid and vapor phases, and in which the point at which the transition occurs is closely confined and controlled; to provide such a device wherein the column is of substantially greater length than diameter, but wherein the current is required to pass through only a relatively short portion of the column; to provide such a device comprising generally a pair of conducting members separated by an insulating section, wherein a thin, relatively fine column of the material extends throughout the members, the arrangement being such that the transition of the material occurs in the relatively short insulating section; to provide such a device wherein the opposite ends of the loading column are subjected to relatively high pressures, so as to assist in the recondensation oi. material from the vapor to the liquid phase; and to provide such devices embodying improved structural relationships of the parts, whereby the manufacture and assembly thereof is facilitated.

With the above as well as other objects in view, which appear in the following description and in the appended claims, preferred but illustrative embodiments of the invention are shown in the accompanying drawing, throughout the several views of which corresponding reference characters are used to designate corresponding parts, and in which:

Figure 1 is a view in longitudinal section of one embodiment of the invention;

Fig. 2 is a view in vertical, transverse section. taken along the line 22 of Fig. 1;

Figs. 3 and 4 are comparative views illustrative of the steps of sealing of! the conducting column of the device in Fig. 1;

Fig. 5 is a view in elevation, partly in section, of a modified embodiment f the invention; and

Fig. 6 is a schematic diagram showing an illustrative application of the device.

As is pointed out in substantial detail in the above identified patents, the features of the present invention are attained primarily by utilizing the property of certain current conducting substances, of which metallic mercury is an example, to change the physical condition or state thereof, when subjected to heat, temporarily to another physical state in which it is either non-conductive or offers a relatively high resistance to current flow. With such a substance, and knowing in advance the average current values to be normally encountered by the device, the substance may be arranged to impart a substantially fixed resistance to current flow of such value that the heat energy derived thereby will cause the conversion of a minute but sufficient quantity of such substance to its relatively non-conductive state, thereby either entirely interrupting or causing a decided decrease in the value of the current flow. The interruption or decrease in the current flow entirely interrupts or materially decreases conduction of heat energy, thereby enabling all or part of the substance which has changed its physical state to revert to its original state, which reversion again initiates or increases the current flow. The current through the device thus pulsates between maximum and minimum values, each increase in current flow producing the above vaporization, and each decrease in current flow resulting in the partial or entire revcondensation of the substance to its original state.

Referring particularly to Figs, 1 and 2, the device, which is designated as a whole as I0, comprises generally a column constituted by axially aligned members I2, I4, and I6, each whereof is pierced so as to define a bore throughout its length. The end portions of the bore are designated I8 and the intermediate portion, which extends through the intermediate section I6, is designated I8a.

Within the broader aspects of the invention, and dependent upon operating requirements, the bore sections I8 may be somewhat larger, or somewhat smaller in diameter than the bore portion Illa, which relative dimensioning appears to control in some degree at least the operating characteristics of the device. The preferred relationship is one wherein the diameters of the bore portions I8 and I811 are substantially the same, and this relationship is shown in the drawing. The sections I2 and I4 are preferably formed of conducting material, and are adapted, by means of clamps or other suitable means 20, for connection at" their ends to terminals 22 of an associated electric circuit. The intermediate section I8 is preferabl formed of non-conducting material. The abutting surfaces of the members I2, I4, and I6 are preferably relatively accurately formed, so that when pressed together, an exceedingly tight seal is formed therebetween, it being noted that if desired, suitable cement may be interposed between the abutting surfaces, so as to perfect the seal, An enclosing envelope 24 preferably surrounds the device and is, of,

course, necessarily formed of insulating material. The sections I2, I4 and I6 are retained in rigidly assembled relation to each other, in the illustrated embodiment, by clamping them between end plates 26 and 28, which are apertured to pass the sections I2 and I4, respectively,

and which abut shoulders 30, 32 formed on these sections. The end plates 26 and 28 are interconnected by one or more rods 34. It will be understood, of course, that the end plates .26 and 28 may be either formed of insulating material or may be otherwise insulated from the sections I2 and I4,'so that the only conducting path through the device, is directly through the sections I2 and 'I4 and through the material filling the bore portions I8 and I811.

As previously stated in the general description given above, the bore portions I8 and I 8a are preferably filled with a material having the property of changing its state from that of a rel-atlv lv good conductor to one which is a relativel poor conductor upon the application of heat. Mercury or mercury amalgam have been found very suitable for this purpose, it being noted that an amalgam formed by adding fivetenths per cent by weight of cadmium to metallic mercury considerably increases the power output and eiilciency of the device. Other elements such as tellurium, gold, silver and the like may'also be used. It will be understood that in the claims, the terms mercury or metal- 110 mercury are used as being generic to mercury and to mercury amalgam.

In the manufactuer of the device, sections l2, I4, and I6 are, of course, accurately aligned with each other and thereafter, following the application of the enclosing envelope 24, are secured in position between the end plates 26 and 28. Thereafter, after carefully cleaning the bore I8, it is preferably completely filled with the mercury. Following the filling operation, the ends of the sections I2 and I4 are sealed off in the manner clearly indicated in Fig. 1. This sealing may, of course, be effected in various ways. A preferred method of accomplishing it comprises initially forming the section such as I2 with an undercut area 35. Following the introduction of the mercury into the bore I8, a

, blunt edged cutting tool may be applied at the undercut area 36, thus separating the extreme end portions I2a from the main body of the sec- .tion i2 and also completely closing the ends of the bore I8.

Various materials may, of course, be employed in the manufacture of the device. In practice, the insulating sections I6 may be formed of glass, plastics, ceramic, quartz or any other durable insulating material which is non-porous, and which is adapted to withstand the relatively high operating temperatures which are encountered in the operation of the device. Similarly, the end sections I2 and I4 may be formed of any suitable conducting materials, steel having been found entirely satisfactory in practice.

Before proceeding with a further statement of the structural features of the above device, its operation may briefly be described as follows. It will be appreciated that the device I0 may be variousl applied to electric circuits, one illustrative arrangement being shown in Fig. 6, wherein the device III, in parallel with a condenser 40, is connected in series with a battery 42 and the primary winding 44 of a suitable transformer T, the secondary winding 46 whereof may be used to supply any suitable load such as the lamp L. A control switch 48 is preferably inserted in the circuit, to control starting and stopping of the device. Upon closure of the control switch 48, the battery 42, of course, becomes effective to apply a voltage across the terminals 20 of the device I0, which voltage causes a current to traverse the circuit. The current flowing through the sections I2 and I4 of the device ID, of course, flows in part through the bodies of these sections and in part through the mercury within the associated parts of the bore portions I8 thereof, By virtue of ,the relatively great cross-sectional area of the metallic body of each section I2 and I4, as compared to the cross-sectional area of the mercury contained in the associated bore parts, a substantial majority of the current flows through the sections I2 and I4. The proportioning of the parts is preferably such that the current traversng the mercury within the bore portions I8 is insuflicient to raise its temperature to the va the liquid phase.

porlzing point. The mercury in such bore portions thus remains in the liquid phase.

n the other hand, all current traversing the device passes through the mercury in the bore Ma 01 the insulating section 16. As set forth above, and as also described in the above identified patents, the proportioning of the parts is such that the passage of the just mentioned current through the short bore section We heats the mercury therein sufiiciently to cause all or part thereof 'to pass into the vapor phase in which it presents substantially greater resistance to the flow of the current than when in This resistance to the flow of the current decreases the value of the current flowing through the device, thereby lessening the heating action, and enabling all or part of the thus vaporized mercury to re-condense into the liquid phase. This lie-condensation sharply reduces the resistance to current flow through the device, resulting in a suificient increase in such current flow to again produce the vaporization. It will be seen, accordingly, that all or part of the mercury contained within the short bore section iila rapidly and recurrently passes between the vapor and liquid phase; and the current flowing in the associated circuit rapidly thus pulsates between maximum and minimum values, which pulsating current is reflected as an alternating current in the circuit associated with the secondary winding 48. In the claims, the sharply increased current is referred to as the normal current and the terms re-condensation or re-conversion are used to refer generically to either the partial or entire re-conversions or re-condensations which follow the abrupt decreases in current flow.

The frequency, applied voltage, reactance of the associated circuit, lengths of the bore sections l6, length of the intermediate bore section i811, and the pressures acting upon the mercury within the bore sections appear definitely related to each other, and variations in each of these factors appear to be accompanied by variations in one or more of the others.

Considering the above factors in more detail, it will be noticed that the provision of the relatively short bore section |8a introduces several important advantages. First, since the mercury within the short section |8a is the only part of the mercury thread which is subjected to sumcient current to vaporize it, all vaporizing and re-condensing cycles occur within such relatively short section. This section is, in general, proportioned so that the length thereof is approximately equal to the length of the vapor bubble which under given pressure conditions is produced during each heating phase. Thus, the vapor bubble is definitely controlled as to position and appears correspondingly definitely controlled as to magnitude. Again, since the current through the device in large part traverses the relatively low resistance bodies of the sections l2 and I4, and encounters a high resistance only when passing through the mercury in the short bore section l8a, it will be appreciated that the power losses in the device are correspondingly minimized and its overall efficiency is increased.

The pressure acting at .opposite sides of the intermediate bore section Illa, which may be termed a loading pressure, appears to be a very significant factor in the performance of the device. As is pointed out in the above Patents Nos. 2,163,708 and 2,163,709, the vaporization of come together reestablishing themaximum conductivity. It is found, however, that the recondensing action is materially improved, and

made more uniform, if a substantial pressure is applied to the vapor, and this substantial pressure also is of material assistance in controlling the initial size of the bubble.

In accordance with the present invention, it is preferred to apply pressures at the opposite sides of the vapor bubble which are substantially in excess of the pressures specifically utilized in the constructions described in the above Patents Nos. 2,163,708 and 2,163,709. The substantially greater pressures preferably utilized in the practice of the present invention increase the operating temperatures of the unit, since, as will be understood, an increase in pressure increases the temperature point at which vaporization of the liquid mercury occurs. ihese increased operating temperatures can, however, be readily taken care of by suitably selecting the materials from which the device is constructed and the materials suggested hereinabove have proved adequate. In the present instance, the relatively high end pressures or loading pressures acting against the vapor bubble are produced in part by providing the relatively long loading column sections 12 and i4, and in part by completely filling these sections with the liquid mercury. One component of the loading pressures results from the physical impedance to flow of the mercury along th relatively long bore sections 18. Another component of the loading pressure is provided by substantially completely confining the mercury thread within the sections [8 and Ma. It is noted that the size of the vapor bubble which appears to be produced is only a very small percentage of the volume of the mercury contained in the two sections l8. The displacement of the liquid mercury required by the formation of the vapor bubble appears to be absorbed in part by an actual compression of the mercury itself and in part by a minute resilient yielding of the confining metal sections l2 and I4. Independently of any specific explanation of the particular manner in which the displaced mercury is absorbed in the system, it is noted that theabove construction produces pressures acting on the vapor bubble which appear to very materially improve its operating characteristics.

The applied voltage, of course, directly affects the performance of the device, since an increase in applied voltage increases the current values passed through it, and consequently, alters the time required to bring the thread to the vaporizing temperature. The reactance of the circuit appears to materially control the performance of the device, particularly in respect to the tendency for an arc to form across the vapor bubble, and also in respect to the time interval required for current values in the circuit to rise and fall between the maximum and minimum values.

With the foregoing general considerations in view, it is noted that in actual practice, devices arranged to be supplied by a six-volt source and to'supply power for operating ten to fifteen foot neon signs through a simple transformer circuit,

have been found to operate satisfactorily, utilizing bore sections l8 and lBa approximately .005 of an inch in diameter; utilizing a bore section |8a approximately .045 of an inch in length; and utilizing loading sections I8 each approximately 1.25 inches in length.

In the modified embodiment of the invention shown in Fig. 5, the device is made up of conducting members 50 and 52 positioned in end-toend relation and separated by an insulating member 54. .As in the first instance, the column thus produced is provided with an axially extending bore 56, the length and diameter whereof is proportioned in accordance with the discussion given above. In this instance, the outer ends of the conducting sections 50 and 52 are of tapered form as indicated at 58, and the conducting sections are provided with complementary members 60 and 62, respectively, which are telescoped over the ends thereof. The members 60 and 62 are counterbored so as to provide relatively large reservoirs such as 64. The outer ends of the end sections 60 and 62 are closed as in the previous embodiment and are arranged to accommodate a terminal such as 66 and 68, by which the device may be connected into the circuit in the relation shown, for example, in Figure 6. The end sections 50 and 52 are provided with shoulders such as 50a, against which the inner ends of the end sections 60 and 62 abut. The latter members in turn are provided with shoulders such as 50a, which receive end plates 68 and 10, which are retained in assembled relation by studs 12. It is preferred, in charging the device with mercury, to introduce sufficient thereof into the bore 56 so as to completely fill both the end reservoirs such as 64. In some cases, the filling operation may leave a minute bubble of gas or air within the reservoirs. It is noted, however, that the virtue of the tapered formation of the ends of conducting sections 50 and 52, the extreme ends of the bore 56 are spaced from the area which such bubbles would occupy in any position of the device. Such bubbles are, therefore, effectively prevented from entering the bore 56, in accordance with the disclosures of the above identified patents.

In the broader aspects of the invention, the structure shown in Fig. distinguishes from the construction shown in Fig. 1 primarily in thatthe column of conducting material, instead of being of entirely uniform diameter throughout its complete length, comprises a mid-section of uniform diameter, and terminates in enlarged reservoirs.

The enlarged reservoirs, as pointed out above, are preferably substantially entirely filled with mercury during the filling operation, so that the space represented by the bore through the column and by the end reservoirs constitutes a substantially solid body of mercury. It is found in practice nevertheless that the enlarged reservoirs have a cushioning effect and in a generic sense, such reservoirs perform the function of providing slightly yieldable pressure applying means.

With this relation, it will be appreciated that a device having the same dimensioning as specifled above with reference to the device of Fig. 1, but also embodying the reservoirs, functions at slightly lower temperatures than the device of Fig. 1, and also has somewhat different output characteristics.

In the embodiment of Fig. 5, the entire device, with the exception of the projecting terminal parts, is encased in a body 14, which may be composed of a suitable ceramic material. The casing 14 serves not only to protect the column structure and assist in perfecting the seal between the abutting surfaces of the members 50, 52, and 54, but also serves to improve the heat radiating characteristics of the device, thereby better enabling it to withstand the relatively high operating temperatures which may be experienced in service. It will be understood that a casing such as 14 may be utilized in connection with the structure of Fig. 1 either in conjunction with or as a substitute for the envelope 24.

It will be appreciated that the foregoing invention provides an extremely simple, economically manufactured, and reliable device for rapidly and recurrently increasing and decreasing current fiow in a circuit and that although only two specific embodiments of the invention have been disclosed, various further modifications in the form, number, and arrangement of parts may be made without departing from the spirit and scope of the invention.

What is claimed is:

1. In a device for rapidly and recurrently increasing and decreasing current flow in an electric circuit, the combination of means defining a passageway, material filling said passageway having the property of being a relatively good conductor at one temperature and of changing its physical state when heated to a higher temperature to one in which it is a relatively poor conductor of current, said passageway being dimensioned so that the normal value of current flowing through the material therein produces sufficient heat energy to cause said change in physical state of a, portion of said material, said means being so constructed and arranged to localize said change in state to a said portion of said material located at a substantially fixed point between the ends of said passageway.

2. In a device for rapidly and recurrently increasing and decreasing current flow in an electric circuit, the combination of means defining a passageway, material filling said passageway having the property of being a relatively good conductor at one temperature and of changing its physical state when heated to a higher temperature to one in which it is a relatively poor conductor of current, said passageway being dimensioned so that the normal value of current flowing through the material therein produces sufficient heat energy to cause said change in physical state of a portion of said material, said means being arranged for connection in an electrical circuit and being so constructed that said change of state is localized to a said portion of material located at a substantially fixed point intermediate the ends of the passageway.

3. In a device for rapidly and recurrently increasing and decreasing current flow in an electric circuit, the combination of means defining a passageway, material filling said passageway having the property of being a relatively good conductor at one temperature and of changing its physical state when heated to a higher temperature to one in which it is a relatively poor conductor of current, said passageway being dimensioned so that the normal value of current flowing through the material therein produces sufficient heat energy to cause said change in physical state of a portion of said material, means enclosing the ends of said passageway so as to define an enclosed space for said material, and said material being introduced in sufficient substantially completely fill said conductor at one temperature and of changing its physical state when heated to a higher temperature to one in which it is aprelatively poor conductor of current, said passageway being dimensioned so that the normal value of current flowing through the material therein produces sumcient heat energy to cause said change in physical state of a portion of said material, means enclosing the ends of said passageway so as to define an enclosed space for said material, and said material being introduced in sufiicient quantities to substantially completely fill said space, said enclosing means being formed to provide resilient cushioning reservoirs at the ends or said passageway.

5. in e. device for rapidly and recurrently in-,

creasing and decreasing current flow in an electrical circuit, the combination of means defining bore, fluid material filling said bore and having the property of being a good conductor when in a fluid state and a poor conductor when in a gaseous state, said bore being'diniensioned so that the normal value of current flowing through the material therein causes the production of heat energy sufilcient to change a part of said material from its fluid to its gaseous state whereby to reduce the fiow oi current through said material, said means being constructed and arranged to localize said change to said gaseous state to a portion of said material located at a substantially fixed point in said passageway.

d. in a device for rapidly and recurrently increasing and decreasing current flow in an electrical circuit, the combination of means defining a bore, fluid material filling said bore and having the property of being a good conductor when in a fluid state and a poor conductor when in a gaseous state, said bore being dimensioned so that the normal value of current flowing through the material therein causes the production of heat energy sufiicient to change a part of said material from its fluid to its gaseous state whereby to reduce the flow of current through said material, said means being connected to an elec-- trical circuit in such relation and being so constructed as to localize said change to a gaseous state to a portion of said material located at substantially a fixed point in said bore.

"7. In a device for rapidly and recurrently increasing and decreasing current flow in an electrical circuit, the combination of means defining a bore, fluid material filling said bore and having the property of being a good conductor when in a fluid state and a poor conductor when in a gaseous state, said bore being dimensioned so that the normal value of current flowing through the material therein causes the production of heat energy sufiicient to change a part of said material from its fluid to its gaseous state whereby to reduce the flow of current through said material, means enclosing the ends of said bore so as to define an enclosed space, and said material being introduced in sufilcient quantity to completely fill said space.

8. In a device for rapidly and recurrently increasing and decreasing current flow in an electrical circuit, the combination of means definin: a bore, fluid material filling said bore and having the property of being a good conductor when in a fiuid state and a poor conductor when in a gaseous state, said bore being dimensioned so that the normal value of current flowing through the material therein causes the production of heat energy sulficient to change a part of said material from its fluid to its gaseous state whereby to reduce the fiow of current through said material, means enclosing the ends of said boreso as to define an enclosed space, and said material being introduced in sufiicient quantity to completely fill said space, said enclosing means formed to provide cushioning reservoirs at the ends of said bore.

9. Ina device for rapidly and recurrently increasing and decreasing current flow in an electrical circuit, the combination of means defining a bore, said means having an intermediate insulating part and conducting end parts, said bore extending through said parts and being of substantially uniform diameter throughout its length, material filling said bore and having the property of being a relatively good conductor at one temperature and having the property of changing its state upon the application of heat to a state in which it is a relatively poor conductor, said bore being dimensioned so that the normal value of current passed through said device causes said change of state, the ends of said means being connected in an electrical circuit so as to pass current through said material.

10. In a device for rapidly and recurrently increasing and decreasing current fiow in an electrical circuit, the combination or" means defining a bore, said means having an intermediate insulating part and conducting end parts, said bore extending through said parts and being of substantially uniform diameter throughout its length, material filling said bore and having the property of being a relatively good conductor at one temperature and having the properties of changing its state upon the application of heat to a state in which it is a relatively poor conductor, said bore being dimensioned so that the normal value of current passed through said device causes said change of state, the ends of said means being connected in an electrical circuit so as to pass current through said material, and means enclosing the ends of said bore, said material being introduced in sufiicient quantity to completely fill said bore.

11. In a device for rapidly and recurrently increasing and decreasing current flow in an electrical circuit, the combination of means defining a bore, said means having an intermediate insulating part and conducting end parts, said bore extending through said parts and being or substantially uniform diameter throughout its length, material filling said bore and having the property of being a relatively good conductor at one temperature and having the properties of changing its state upon the application of heat to a state in which it is a relatively poor conductor, said bore being dimensioned so that the normal value of current. passed through said device causes said change of state, the ends of said means being connected in an electrical circuit so as to pass current through said material, and means enclosing the ends of said bore, said material being introduced in suflicient quantity to completely fill said bore, and means for applying loading pressures to the material in said bore so as to cause said re-condensation of said material.

? creasing and decreasing current flow in an electric circuit, the combination of means defining a passageway, material filling said passageway having the property of being a relatively good conductor at one temperature and of changing its physical state when heated to a higher temperature to one in which it is a relatively poor conductor of current, said passageway being dimensioned so that the normal value of current flowing through the material therein produces sufficient heat energy to cause said change in physical state of a portion of said material, said means being so constructed and arranged that said change 01 state occurs at a substantially fixed point between the ends of said passageway, and means for applying loading pressures to the material in said passageway so as to cause at least partial reconversion of said portion of said material to its original state.

18. In a device for rapidly and recurrently increasing and decreasing current flow in an electrical circuit, the combination of means defining a bore, fluid material filling said bore and having the property of being a good conductor when in a fluid state and a poor conductor when in a gaseous state, said bore being dimensioned so that the normal value of current flowing through the material therein causes the production 0! heat energy suflicient to change a part of said material irom its fluid to its gaseous state whereby to reduce the flow of current through said material, said means being so constructed and arranged that said change to said gaseous state occurs at a substantially fixed point in said passageway, and means for applying loading pressures to the material in said bore so as to cause at least a partial reconversion of said part of said material to said fluid state.

JOHN M. HEDDAEUS. 

